This application claims the priority benefit of Taiwan application serial no. 89117743, filed Aug. 31, 2000.
1. Field of the Invention
The present invention relates to a temperature controlling protection system for a heater of a wet etching device. More specifically, the present invention relates to a temperature controlling protection system, especially useful for the heater of the wet etching device when a failure occurs and increases the temperature to an exceptionally high value.
2. Description of the Related Art
Wet etching is one of the earliest techniques to have been developed in the semiconductor manufacturing industry. Wet etching is carried out by reaction between films and specific solutions to remove the films not covered by photo resist. Wet etching technology is advantageous because it is simple and fast. The main parameters for control of the reaction of the wet etching include concentrations of solutions, etching time period, temperature for reaction, and method selected for agitating the solutions. Since the wet etching is a chemical reaction, the higher the removing rate of films, the higher the concentration of etching solution or the temperature for etching reaction. However, excessively high etching rate of films results in significant cutting. Accordingly, these two conditions have to be controlled appropriately.
As shown in FIG. 1, which is a block diagram showing a heater of a conventional wet etching device, controlled reaction temperature for wet etching is illustrated as follows. The wet etching device includes a control unit 10, a heating ON/OFF controller 12 and a heater 18. The control unit 10 is connected to the heating ON/OFF device 12 that is connected to the heater 18. The control unit 10 can be a Central Processing Unit (CPU) or a Programming Logical Controller (PLC) to receive control signals, such as a level signal for a level sensor (not shown), an overheated signal for a temperature sensor (not shown), a ON/OFF signal for acid discharging switch (not shown), a protection signal and a caution signal for the heater 18 and an output signal for a constant temperature controller (not shown) from a sensor or a switch. The control unit 10 determines whether these control signals are normal or abnormal to ensure the starting of the heater 18 of the wet etching device.
When the control unit 10 determines that the control signals are normal, signals are output to the heating ON/OFF controller 12. The electromagnetic contactor 16 in the heating ON/OFF device 12 is used to receive these signals to actuate the solid state relay 14 of the heating ON/OFF controller 12. The solid state relay 14 thus provides power to the heater 18 of the wet etching device.
The control unit 10 judges the signals, such as a level signal for a level sensor, an overheat signal for a temperature sensor, an ON/OFF signal for an acid discharging switch, a protection signal and a caution signal for the heater and an output signal for a constant temperature controller as normal or abnormal, and actuates the heater 18 of the wet etching device depending the results of judgement. When the temperature of the gas in the wet etching device is excessively low, the control unit 10 outputs a signal to start the heater 18. If the heater 18 continues running because the control unit 10 occurs failure; however, there is a rise in risk caused by the exceptionally high gas temperature of the wet etching device if the heater 18 fails to be turned off.
Therefore, the present invention provides a temperature controlling protection device for the heater of the wet etching device. The prior problem of the control unit failure and failure to control the heater of the wet etching device can be eliminated to ensure operation safety in the following process.
The present invention provides a temperature controlling protection system for the heater of the wet etching device, comprising a control unit, a temperature controlling protection device and a heating ON/OFF controller. The control unit is used to receive a sensed signal and output a control signal. The temperature controlling protection device is used to receive such a sensed signal and output a temperature controlling signal according to the sensed signal including a plurality of condition signals. The heating ON/OFF controller coupled to the control unit and the temperature controlling protection device are used to receive the above-mentioned control signals so as to control the power of the heater to change the ON/OFF state of the heater.
The present invention provides a temperature controlling protection system for the heater of the wet etching device, comprising a control unit, a first heating ON/OFF controller, a temperature controlling protection circuit and a second heating ON/OFF controller. The control unit is used to receive a sensed signal and output a control signal. The first heating ON/OFF controller is used to receive the control signal from the above control unit so as to control the power of the heater. The temperature controlling protection circuit is used to receive the sensed signal and output a temperature controlling signal according to the sensed signal including a plurality of condition signals. The second heating ON/OFF controller is used to receive the control signal from the temperature controlling protection circuit so as to control the power of the heater.
In the above temperature controlling protection system for the heater of the wet etching device, the condition signals of the temperature controlling signal include a level signal for a level sensor, an overheated signal for a temperature sensor, an ON/OFF signal for an acid discharging switch, a protection signal and a caution signal for the heater and an output signal for a constant temperature controller.
The above heating ON/OFF controller further includes an electromagnetic contactor and a solid state relay.
The temperature controlling protection system for the heater of the wet etching device of the present invention can be the second measure for protection of the heater when the control unit has a failure. The structure of the heating ON/OFF controller of the temperature controlling protection device and the heating ON/OFF controller of the main loop constructed in series can be used to shut down the heater to effectively prevent continuous heating, when the heater continues running to result in an excessively high temperature in the wet etching device. Operation safety can be thus ensured when the process is performed in the plant.